In cable modem systems, there is a need to be able to debug by capturing message and burst traffic in the upstream and downstream directions. In DOCSIS systems, there is a need to be able to capture all the data bursts, MAP and UCD messages, timestamp data, ranging request messages, ranging bursts, ranging response messages and all the other DOCSIS messages.
Sniffers exist in the prior art. A DOCSIS traffic sniffer manufactured by Filtronic-Sigtek, Inc. (model number ST260B) can captures data bursts and message traffic in DOCSIS 1.0 and 1.1 systems. However, DOCSIS 2.0 systems include the ability to send spread spectrum bursts, and the Filtronic sniffer cannot capture and demodulate spread spectrum bursts and time division multiplexed bursts at symbol rates faster than symbol rates of DOCSIS 1.0 and 1.1 systems. This device does not appear to be covered in any patents or published patent applications.
Conventional sniffers today are too complicated. It would be advantageous to have a simple DOCSIS 2.0 sniffer which can use a conventional DOCSIS 2.0 cable modem that has been modified to provide timing and control signals for a burst capture circuit that captures upstream bursts. It would also be advantageous to divert upstream bursts away from a CMTS and capture them in such a sniffer and provide such a sniffer with the capability to repeat captured bursts upstream so that only bursts and upstream messages are transmitted upstream and nothing else is transmitted. This could replace the digital return prior art where everything going upstream including empty minislots is digitized and sent upstream as digital samples. Both digital return systems in the prior art and a digital upstream sniffer/repeater allow the CMTS to not have any burst acquisition circuitry and only use digital signal processing circuitry to process the digital samples. This simplifies the CMTS. However, a digital sniffer/repeater which transmits upstream only bursts and messages allows greater consolidation of upstream traffic from different optical nodes and allows the CMTS to be used more efficiently.
Accordingly, a need has arisen for a sniffer which can capture all types of DOCSIS bursts including SCDMA DOCSIS 2.0 bursts in both the upstream and downstream. There has also arisen a need for a simpler DOCSIS 2.0 upstream only sniffer and a simpler DOCSIS 2.0 upstream only sniffer with repeater capability.